In a pair of letters sent to CIA Director John Brennan and Attorney General Eric Holder, Reid backs Feinstein’s account of events, calling the CIA’s counter-accusation “absurd” and accusing the agency of having “seemingly attempted to intimidate its overseers by subjecting them to criminal investigation.”

Last Tuesday, Feinstein gave a speech on the Senate floor accusing the agency of violating the law and the Constitution by breaching computers set up for Senate intelligence committee staff conducting an investigation into the Bush-era rendition and interrogation program. CIA Director John Brennan denied that the agency had done anything wrong, but did not dispute that the search had occurred. The CIA Inspector General recommended the Justice Department look into whether any laws were broken. The CIA’s acting general counsel at the time, Robert Eatinger, also asked the Justice Department to look into whether Senate staff had somehow gained unauthorized access to classified material.

The Senate report on Bush-era torture has not yet been declassified, but is said to be highly critical of the CIA, concluding that the interrogation program was ineffective. Feinstein accused the CIA of trying to undermine the report by denying the Senate staff access to an internal report commissioned by then-CIA Director Leon Panetta, which came to similar conclusions as the Senate investigation–and which contradicted the CIA’s rebuttal of the Senate’s work. The CIA has said they were concerned about disclosure of classified information.

“You are no doubt aware of the grave and unprecedented concerns with regard to constitutional separation of powers this action raises,” Reid wrote of the CIA’s search in his letter to Brennan. ”To my knowledge, the CIA has produced no evidence to support its claims that Senate committee staff who have no technical training somehow hacked into the CIA’s highly secure classified networks, an allegation that appears on its face to be patently absurd.” Reid asks that Brennan allow the Senate’s chief law enforcement official, Sargeant-at-Arms Terrance Gainer, to “initiate a forensic examination” of the computers and the network used by the Senate intelligence committee staff.

In his letter to Holder, Reid writes that “the CIA cannot be permitted to undermine Congress’s ability to serve as an effective check on executive power as our nation’s Founders intended,” adding that “I trust you will carefully examine these concerns as the Department of Justice determines how to proceed.”

The Justice Department has seemed apprehensive about wading into the tensions between the Senate and the CIA. At a news conference Wednesday, Holder said “We get referrals all the time. The fact that we get a referral does not necessarily mean we make a decision that we’re going to investigate on the basis of that referral.”